6.6. Compatibility with Older Systems

If an ACL has been set on any file on a given file system, that file
system has the ext_attr attribute. This attribute
can be seen using the following command:

tune2fs -l <filesystem-device>

A file system that has acquired the ext_attr
attribute can be mounted with older kernels, but those kernels do not
enforce any ACLs which have been set.

Versions of the e2fsck utility included in version
1.22 and higher of the e2fsprogs package (including
the versions in Red Hat Enterprise Linux 2.1 and 4) can check a file system with
the ext_attr attribute. Older versions refuse to
check it.